E.4 Heparin Induced Thrombocytopenia.

Question 1

Prothrombotic disorder associated with unfractionated heparin (UFH) or low molecular weight heparin. (LMWH)

Answer 1

Heparin Induced Thrombocytopenia (HIT)

Question 2

Is HIT more common with UFH or LMWH?

Answer 2

Unfractionated Heparin (5% vs 0.5-1%)

Question 3

HITT

Answer 3

HIT complicated by thrombosis.

Question 4

What factors increase the risk of HIT?

Answer 4

1. Bovine Heparin (vs porcine)
2. UFH (vs LMWH)
3. Surgical Patients
4. Longer Exposure
5. IV administration

Question 5

4 Ts Score:
Platelet Drop 50+%
and
Nadir >20,000

Answer 5

2 points

Question 6

4 Ts Score:
Platelet Drop 30-50%
or
Nadir 10,000-20000

Answer 6

1 Point

Question 7

4 Ts Score:

Symptoms occur within 5-10 days of exposure or 1 day with previous exposure.

Answer 7

2 points

Question 8

4 Ts Score:
Symptoms occur within 1 day with exposure over 30 days ago or symptoms occur within 10 days after exposure.

Answer 8

1 point.

Question 9

4 Ts score

Symptoms occur in less than or equal to 4 days without previous exposure.

Answer 9

0 points.

Question 10

4 Ts Score:

New Thrombosis since starting therapy.

Answer 10

2 Points

Question 11

4 Ts Score:
Progressive or recurrent thrombosis since starting therapy.

Answer 11

1 Point

Question 12

4 Ts Score:
Thrombosis suspected or no new thrombosis.

Answer 12

0 points.

Question 13

4 Ts Score:

No possible explanation for platelet decline besides HIT.

Answer 13

2 points

Question 14

4Ts score:

There could possibly be other causes of HIT

Answer 14

1 Point

Question 15

4-T Score of <3

Answer 15

Low Probability of HIT

Question 16

4-T Score 4-5

Answer 16

Intermediate Probability of HIT

Question 17

4-T Score of 6-8

Answer 17

High Probability of HIT

Question 18

What are the 4-Ts

Answer 18

Thrombocytopenia, Timing, Thrombosis, The Cause of Decline

Question 19

Based on the 4-T Score when should we stop all heparin?

Answer 19

When the score is not low (<3).

Question 20

What other tests for HIT are recommended based on laboratory capabilities?

Answer 20

1. PF4 IgG Elisa Immunoassay
2. Serotonin Release Assay

Question 21

What are the available non-heparin coagulants to use in HIT?

Answer 21

1. Argatroban
2. Bivalirudin
3. Fondaparinux
4. DOACs

Question 22

What is the preferred DOAC to use in HITT?

Answer 22

Rivaroxaban (Xarelto)

Question 23

Xarelto HIT Dose

Answer 23

15 mg BID until platelet count recovery (>150,000), then 20 mg QD.

Question 24

Xarelto HITT Dose

Answer 24

15 mg twice daily for 3 weeks, then 20 mg QD.

Question 25

What is the goal aPTT with Argatroban and Bivalirudin?

Answer 25

1.5-3X ULN

Question 26

When using a direct thrombin inhibitor, at what point is it proposed to switch to warfarin?

Answer 26

Once the platelet count reaches >150,000.

Question 27

Does Argatroban or Bivalirudin effect INR to a greater extent?

Answer 27

Argatroban

Question 28

What is the protocol for switching from Argatroban to Warfarin?

Answer 28

1. Administer 5 doses of Warfarin
2. If INR >4 consider stopping Argatroban.
3. Recheck PTT/INR after 2-4 Ours

4a. If in range–> leave Argatroban off.

4b. below range–> add argatroban and increase warfarin dose.

Question 29

What is the protocol for switching from bivalirudin to warfarin?

Answer 29

1. Administer 5 doses of warfarin.
2. If INR >3 consider stopping bivalirudin.
3. Recheck PTT/INR in 2-4 hours.

4a. In range–> leave bivalirudin off.

4b. below range–> restart bivalirudin and increase warfarin dose.

Question 30

What is the protocol for switching from DTI to a DOAC?

Answer 30

There isn’t one, just stop the DTI.

Question 31

Duration of HIT Therapy

Answer 31

30 days

Question 32

Duration of HITT Therapy

Answer 32

3 months.